The best cross-platform framework is Xamarin. Xamarin is an open-source platform that allows developers to create native apps for multiple platforms using a single codebase. It supports iOS, Android, Windows, and MacOS, allowing developers to quickly and easily create apps for multiple platforms. Xamarin also offers a range of tools and features to make development easier, including a powerful UI designer, powerful debugging tools, and a library of pre-built components. It also offers integration with popular cloud services such as Microsoft Azure.